The present invention relates to a cooling system for a vehicle, the system comprising a first cooling circuit coupled to the vehicle engine for cooling the latter, a pump arranged in the first cooling circuit for pumping a coolant to the engine, a second cooling circuit for cooling at least one other component in the vehicle, and means of coupling the second cooling circuit into the first cooling circuit in order to also supply the second cooling circuit with coolant from the pump.
Such a cooling system may be used, for example, in a work vehicle, such as a wheel loader, which comprises hydraulic components in the form of working cylinders, for example, for maneuvering/moving an implement. With regard to the hydraulics, it is primarily the hydraulic oil and gaskets, seals, etc. which are temperature sensitive.
According to a previously known system the coupling means consists of a thermostat, which is operatively controlled by the engine temperature to cut in automatically when the engine temperature exceeds a certain value.
According to this previously known system just one pump is used to provide cooling both for the vehicle engine and for the hydraulic components of the vehicle. One problem with this system is that under certain conditions the thermostat will not cut in, with the result that the hydraulic components do not receive the necessary cooling. One example of this occurs in an extremely cold climate when the vehicle is used in such a way that its hydraulic components become so hot that cooling is required, whilst the engine is not hot enough for the thermostat to cut in.
The cooling system may furthermore be designed to cool transmission components in the form of gears and shafts in the vehicle axle housings, for example, via the second cooling circuit. A problem with this system is that under certain operating conditions the thermostat will not cut in, with the result that the transmission components do not receive the necessary cooling. An example of this is in so-called leveling, when a mass of earth is pushed ahead of the vehicle. In this application the transmission becomes hot, whilst the engine is cold.
A further problem with the previously known system is that if the thermostat fails and does not or is not open, there is no cooling at all of the hydraulic or transmission components.
The temperature limit at which the thermostat cuts in is controlled by the engine exhaust. Owing to the ever more stringent requirements governing vehicle exhaust emissions, this temperature limit is also increasing. It is therefore not just simply a matter of adjusting the temperature limit for a specific vehicle to a lower value in order to also provide the second circuit with coolant.
The invention will be described below in its application to a work vehicle in the form of a wheel loader. This is to be regarded as a preferred application but is in no way limitative. The invention can be realized, for example in other types of work vehicle, such as a dumper truck or excavator-loader, for example. The invention is furthermore not confined to work vehicles, but could also be applied to other types of vehicle, such as industrial trucks.
The term disconnected position signifies that the coupling means is not set to connect the first and second circuits.
In accordance with an aspect of the present invention, a cooling system for a vehicle comprises a first cooling circuit coupled to the vehicle engine for cooling the engine, a pump arranged in the first cooling circuit for pumping a coolant to the engine, a second cooling circuit for cooling at least one other component in the vehicle, means for coupling the second cooling circuit into the first cooling circuit in order to also supply the second cooling circuit with coolant from the pump when the coupling means is in a connected position, and a bypass line coupled from the first cooling circuit to the second cooling circuit bypassing the coupling means, so that the second cooling circuit is supplied with coolant from the pump via the bypass line even when the coupling means is in a disconnected position.
In accordance with another aspect of the present invention, a cooling system for a vehicle comprises a first cooling circuit coupled to the vehicle engine for cooling the engine, a pump arranged in the first cooling circuit for pumping a coolant to the engine, a second cooling circuit for cooling at least one other component in the vehicle, a thermostat for coupling the second cooling circuit into the first cooling circuit in order to also supply the second cooling circuit with coolant from the pump when the coupling means is in a connected position, and a bypass line coupled from the first cooling circuit to the second cooling circuit bypassing the thermostat, so that the second cooling circuit is supplied with coolant from the pump via the bypass line even when the thermostat is in a disconnected position.
In accordance with a further aspect of the present invention, a vehicle comprises a cooling system of the type described above.